Oxidation dyes have attained substantial importance in the field of keratin fiber dyeing and particularly hair dyeing. The color is generated by reaction of certain developers with certain couplers in the presence of an appropriate oxidant. The developers used for this purpose are, in particular, 2,5-diaminotoluene, 2,5-diaminophenylethyl alcohol, p-aminophenol, 1,4-diaminobenzene and 4,5-diamino-1-(2-hydroxyethyl)pyrazole, whereas suitable couplers are, for example, resorcinol, 2-methylresorcinol, 1-naphthol, 3-aminophenol, m-phenylenediamine, 2-amino-4-(2′-hydroxyethyl)aminoanisole, 1,3-diamino-4-(2′-hydroxyethoxy)benzene and 2,4-diamino-5-fluorotoluene
In addition to being able to produce colors of the desired intensity, oxidation dyes used for dyeing human hair must meet many other requirements. For example, such dyes must be unobjectionable from a toxicological and dermatological standpoint, and the hair colorations obtained must be highly resistant to light, permanent waving, acids and rubbing. In any case, however, they must remain stable for a period of at least 4 to 6 weeks without the influence of light, rubbing and chemical agents. Moreover, it must be possible, by a combination of suitable developers and couplers, to produce a wide range of different color shades.
Although many couplers are already known, with the currently known colorants it is not possible to meet the requirements placed on a colorant in every respect. Hence, a need continues to exist for novel couplers that will meet the aforesaid requirements to an especially high degree.